When conducting forensic examinations to solve a crime, it is often necessary to compare the image of a first sample to the image of a second sample to obtain further details about the course of a crime.
Thus, for example, the impressions on cartridge cases caused by the firing pin of a weapon are compared to each other to determine whether the same weapon was used in two or more crimes.
Another known use of optical comparative examinations is to verify the authenticity of documents, in particular, of banknotes to ascertain whether they are forged.
Finally, to solve crimes, it is often necessary to compare fibers from clothes found at the crime scene to fibers from known pieces of clothing to be able to draw conclusions on the clothing worn by a perpetrator during a crime.
The applicant sells forensic comparison microscopes and comparison macroscopes, which are composed of two separate microscopes or separate macroscopes joined by a bridge, and which are suitable for performing the forensic comparative examinations mentioned above. The bridge contains a device which is used to combine the two separate images produced by the separate microscopes/macroscopes, and which is generally designed as a beam splitter known in optics for a long time. The two images of the separate microscopes/macroscopes to be compared are combined by the beam splitter in such a manner that, when viewed by the operator of the comparison microscope/macroscope through a shared tube mounted on the bridge, the two images are perceived as superimposed. By masking corresponding subareas of the two samples, a composite image is formed which allows direct comparison, for example, of one half-sample to the other half-sample.
Beam splitters which are used for both splitting and combining beams of light are described, for example, in “Bauelemente der Optik” [Optical Components], Taschenbuch für Konstrukteure [Handbook for Engineers], 4th revised edition, H. Naumann/G. Schröder, pp. 186 through 188.
The known comparison microscopes/macroscopes have the problem that, due to the design of the known beam-splitters in the tube, the perception of two separate images to be compared is not neutral in color, which makes it considerably more difficult to compare the two samples and, because of the missing or at least very limited color information, also unnecessarily reduces the reliability with which two probes can be identified.